Studies On The Preparation Of Molecularly Imprinted Polymer Microspheres On The Surface Of Ordered Macroporous SiO₂ And Their Molecular Recognition Properties

Three-dimensionally ordered macroporous?3DOM?material is a new type of porous material with uniform pore diameter,great surface area,high porosity and photonic bandgap,and has been widely used in separation science,catalytic carrier and photonic crystals.Molecular imprinting technology provided a method to prepare the polymers with specific recognition to the special template molecule.The prepared molecularly imprinted polymers?MIP?have been used in the separation,sensors,and enzymatic catalysis and so on,and show a wide application prospect.In this paper,the macroporous molecularly imprinted composite microspheres with specific recognition ability are prepared by combining three-dimensionally ordered macroporous materials and surface molecular imprinting techniques using the biological macromolecules bovine hemoglobin and Chinese medicine effective molecule glycyrrhizic acid as template.The polymeric microspheres have both the high permeability of the ordered macroporous material and the recognition characteristics of the molecularly imprinted material,which solve the deficiency of traditional imprinted polymers,such as slow mass transferring rate and low recognition efficiency.Therefore the study broadens the application range of the molecularly imprinted materials.The specific contents of the study are including as follows:The first section:The three dimensional ordered macroporous SiO₂ microspheres were prepared in water/oil suspension system by a codeposition method using polyacrylamide?PAM?microspheres as colloidal crystal template and silica nanoparticle as skeleton units.The preparation conditions of PAM colloidal crystal microspheres,the codeposition temperature,the solid phase volume ratio of SiO₂/PAM,the rotating rate and the removing methods of colloidal crystal template were studied.The results show when the codeposition temperature is 80?,the solid phase volume ratio of SiO₂ is 9.08%,the rotating speed is 100 r/min,the removal of colloidal crystal template was by combining water soaking and calcinations,the prepared macroporous SiO₂ particles have a uniform spherical shape and good mechanical strength.The scanning electron microscope?SEM?shows the microspheres have a closely packed structure.The macropores were very good internal replication of the PAM colloidal crystal template,and have a ordered pore structure with a shrinkage of 2.5%.Nitrogen adsorption/desorption experiments and the porosity measurements show the macroporous material have a high specific surface area(128.67m² g^-1)and porosity?77.04%?.The second section:The MIP was successfully grafted onto the surface of the KH570-modified macroporous SiO₂ microspheres by using biomacromolecule bovine hemoglobin?BHb?as the imprinting molecule,acrylamide?AM?as the functional monomer,N,N'-methylenebisacrylamide?MBA?as the cross-linking agent,ammonium persulfate?APS?as the initiator,20%ethanol-phosphate buffer?pH 6.2,10 mM?as the porogen.The prepared polymer composite microspheres were characterized by SEM,thermogravimetric analysis?TG?,infrared spectroscopy?FT-IR?and BET analysis.The results show the diameter of the modified macroporous SiO₂ microspheres is becoming smaller after grafting and the grafting amount of the polymer is about 30.98%.The imprinted composite microspheres have the rigidity of SiO₂ and the flexibility of PAM hydrogel and show high mechanical strength and good swelling resistance.Kinetic experiments showed the surface imprinted microspheres had a faster binding kinetics rate for imprinted molecules and their binding constants were about 7 times higher than those of the traditional MIP.The selective experiment showed that the surface imprinted microspheres had good recognition ability to the target protein?BHb?,and the imprinting factor reached 3.20.The third section:Two types of molecularly imprinted materials were prepared by using the bulk polymerization method and the surface imprinting method on the KH570-modified macroporous SiO₂ microspheresby using the traditional Chinese medicine effective molecule?glycyrrhizic acid,Gly?as the template molecule,methacrylic acid?MAA?as functional monomer,ethylene glycol dimethacrylate?EDMA?as cross-linking agent,azobisisoheptonitrile?ABVN?as initiator,N,N-dimethylformamide?DMF?as porogen,respectively.The isothermal adsorption and kinetic binding behaviors of the two polymer materials were compared.The results showed that both imprinted polymers showed specific recognition properties for the imprinted template when the molar ratio the of Gly/MAA/EDMA was 1:32:50.However,the macroporous surface imprinted polymer microspheres indicated higher adsorption rate and the imprinting efficiency than the bulk polymer materials.